Wireless telephones, such as mobile/cellular telephones, cordless telephones, and other consumer audio devices, such as mp3 players, are in widespread use. Performance of such devices with respect to intelligibility can be improved by providing noise cancelling using a microphone to measure ambient acoustic events and then using signal processing to insert an anti-noise signal into the output of the device to cancel the ambient acoustic events.
A stereo headset with one or two microphones and a speaker per ear, coupled to a personal audio device, such as a wireless telephone, cordless telephone, or other consumer audio devices, may include an adaptive active noise cancellation (ANC) circuit that is not co-located with transducers associated with the ANC circuit, such as microphones and speakers, thus forming a “distributed” ANC system in which the adaptive ANC circuitry is separated from the transducers by a digital link. In some circumstances, the digital link may become unreliable or fail. In such case, the communication between the transducers and the adaptive ANC circuitry may be interrupted. In such a scenario, erroneous data may be passed between the adaptive ANC circuitry and the transducers, or the data may cease altogether. Accordingly, it may be desirable to prevent objectionable audible artifacts that may occur as a result of failure or unreliability of the digital link.